var num = 1
let obj = {
  num: 2,
  add: function () {
    this.num = 3
    ;(function () {
      console.log(this.num)
      this.num = 4
    })()
    console.log(this.num)
  },
  sub: function () {
    console.log(this.num)
  },
}
obj.add()
console.log(obj.num)
console.log(num)
const sub = obj.sub
sub()
